This application describes an investigation of the larynx centering on its physiological control and role as a source function for speech. The research method aims at revealing the relationship between the controlling muscular and aerodynamic forces, a the resulting configurational and vibratory adjustments, and the final acoustic output. Muscular activity will be studied by electromyographic techniques; plethysmography will be used for estimating lung volume; aerodynamic data will consist of sub- and supra-glottal pressure and flow measurements; aspects of laryngeal configuration will be examined by comparing data from fiberoptic images, high-speed movies, glottal transillumination, and electroglottography; a coustic measures will include use of inverse filtering. A practical goal of many of the comparative measurements is to develop noninvasive methods of assessing laryngeal function that can be used to replace more direct, but necessarily invasive techniques. An understanding of speech function requires an understanding of glottal abduction and adduction, the control of fundamental frequency, and the control of glottal configuration, because these area fundamental parameters that govern segmental manner distinctions, suprasemental control, and voice quality control. As part of this general account, the larynx-vocal tract interaction is examined from two points of view--first, temporally in segmental articulation, and second, aerodynamically and mechanically as they interact in FO and voice quality control. Studies on normal speakers are to be paralleled by studies of three clinical populations, the deaf, fluent and dysfluent aphasics, an stutterers. The object of these studies is to provide information about mechanisms that may prove useful in remediative therapy.